In a conventional indoor unit of an air conditioner, a rear drain pan for receiving drain from a rear side heat exchanger is provided on a rear plate that is placed on rear side of a blower fan and that guides to a blowoff opening air having passed through a front and the rear side heat exchangers (e.g., JP 8-14596 A).
In an indoor unit of an air conditioner, which is not shown, a rear plate of the unit is molded in one piece so as to have a cross-section generally shaped like a letter Y, and a rear drain pan is formed of a portion of the plate which has the Y-shaped cross-section. Specifically, the rear plate is composed of facing part that faces a blower fan and protruding part that protrudes rearward from lower end of tongue part that is upper end part of the facing part, and the rear drain pan formed of the tongue part and of the protruding part is molded in one piece from resin, so that production cost therefor is reduced.
Incidentally, the rear plate is molded with use of a lower metal mold that has a large cross-sectional area and that is for molding a front side of the facing part for guiding air and an upper metal mold that has a small cross-sectional area and that is for molding an inner surface of the rear drain pan. The lower metal mold having the large cross-sectional area and thus allowing penetration therethrough of a large number of cooling pipes can sufficiently be cooled by those pipes, whereas the upper metal mold having the small cross-sectional area and thus allowing penetration therethrough of few cooling pipes cannot be cooled sufficiently, which causes a great difference in temperature between resin part of the tongue part in contact with the lower metal mold and resin part of the tongue part in contact with the upper metal mold. The great temperature difference results in a problem in that an excessive residual stress in the tongue part that is the upper end part of the rear plate may cause a warp of the upper end part of the rear plate after release of the molds.